An improved formulation of the ripple-averaged kinetic theory of neoclassical transport in stellarators
The ripple-averaged kinetic theory of neoclassical transport in multiple-helicity stellarators is presented anew, using a formulation, which ameliorates several shortcomings of the conventional approach. In particular, during the averaging procedure the usual simplifying assumptions of symmetric local ripples and "small" rotational tranform per field period are avoided through an appropriate choice of coordinate system and local model for the magnetic field strength; averages are truly performed along a field and not along the toroidal-angle coordinate, as is common. Phase space divides naturally into three portions in which particles are locally trapped, locally reflected but not trapped, and locally passing. The second of these is lacking the conventional description. As an example of the theory's many possible applications, the monoenergetic radial transport coefficient in the symptotic 1/v regime is derived and radial profiles of the quantity are determined for the Large Helical Device and Wendelstein 7-X. The results are compared with those obtained using the conventional approach. Significant differences are found in the case of Wendelstein 7-X and verified numerically using the Drift Kinetic Equation Solver (DKES).
Bibliographic Reference: An article published in: Plasma Physics and Controlled Fusion, Vol.43 (2001), pp.1131-1148
Record Number: 200113881 / Last updated on: 2001-10-09
Original language: en
Available languages: en